If you're switching from Outlook to Lotus Notes, you must convert PST to NSF file format. IBM Lotus Notes provides you a freeware tool, called nUpgrade.exe utility. It's a part of Lotus Notes migration tools. By using this utility, you can successfully import mailbox content from PST file to new NSF file without requiring any 3rd party tool. Refer to this article for some useful information - Import Outlook to Lotus Notes – Convert PST to NSF

Before you can purchase any paid software to convert PST to NSF format, you must use the nUpgrade.exe utility.